Re: Rewrite MAC-adr on outgoing packages?
[...]
JE> Proxy-arp does do something similar to bridging. Probably not
JE> the same, but I am not exactly sure about it. Is anyone?
Yes. In the part I deleted, you outlined what a bridge does (bridge
at the ethernet layer). I'll be brief as there are authoritative
sources for these (networking textbooks!):
ARP: I know what IP address I want to send this packet to, I know
what ethernet interface that IP address is at but I don't know what MAC
address to send it through that ethernet interface. I do an ARP query
"who has <this IP address> tell me" _on that etherenet_ and the owner
of <this IP address> says "<this IP address>'s MAC address is this."
Now I know how to get the packet to that IP. This happens all the
time with the results cached for anywhere from minutes to hours (4hrs
is default on Cisco's for example).
Proxy ARP: I am a router with two ethernet interfaces, eth1 and eth2
with networks n1 and n2 respectively. Someone on eth1 makes an
ARP query (see above) for an address a2 in n2, now _I_ say
"a2's MAC address is M" on eth1, where M is _my_ MAC address. So the
packet comes to me, and I forward it to the proper machine on eth2.
The "who has ..." stuff is not baby talk I made up, if you sniff the
wire with tcpdump, it'll actually interpret ARP stuff and display
the "who has..." etc questions.
cheers,
BM
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